The long-term goal of this application is to explain individual differences in susceptibility to addictive drugs. The hypothesis that guides the research is that individual differences in decision making contribute to individual differences in drug use. The specific aims of the research are to answer the following questions: Do individual differences in decision making predict smoking cessation? Do differences in decision making help explain the high correlations between substance dependence and other psychiatric disorders? And to what extent are differences in decision making correlated with differences in impulsivity and cognition? The studies use a computer-based procedure in which choices earn money. The salient features of the task are that current choices alter the consequences of future choices, and that one option is best from the perspective of the current trial (the "local" solution), whereas the other option is best from the perspective of two or more trials (the "global" solution). According to some theories, these conditions are similar to the situation facing a drug user. From a local perspective, drug use may be the best choice, but from a global perspective, alternatives to drug use are usually the better choice. The first set of studies tested drug clinic patients. Choice behavior was correlated with drug use history. Preference for the local solution in the experimental procedure predicted long-term illicit drug use and the persistence of smoking. Drug clinic and control groups differed in terms of education and IQ, but these two measures were not as strongly correlated with the pattern of choices as was drug history. The proposed studies will test the generality of the initial results and test hypotheses concerning the psychological factors that influence decision-making. The findings will help clinicians target behaviors that are instrumental in the persistence of drug use.